Flying printer

ABSTRACT

A FLYING PRINTER HAVING A TRIGGEL LEVER ADAPTED FOR ROTATIONAL AND LINEAR DISPLACEMENT, A PRINT HAMMER ADAPTED TO EFFECT PRINTING IN RESPONSE TO THE LINEAR DISPLACEMENT OF SAID TRIGGER LEVER, A CONTINUOUSLY ROTATING RATCHET WHEEL HAVING AT LEAST ONE TOOTH EXTENDING THERFROM FOR LINEARLY DISPLACING SAID TRIGGER LEVER WHEN SAID TRIGGER LEVER IS DISPOSED IN THE PATH THEREOF, AND MEANS FOR SELECTIVELY ROTATING SAID TRIGGER LEVER INTO AND OUT OF THE PATH OF SAID RATCHET WHEEL TOOTH TO EFFECT PRINTING.

lSSEl IMAHASHI FLYING PRINTER Nov. 30, 1971 6 Sheets-Sheet 1 Filed Apiia. 29; 3%9

FLYING PRINTER 6 Sheets-Sheet 112 Filed Apri 1 719, 1969 NOV. 1971 ISSEIIMAHASHI 3,623,428

FLYING PRINTER Filed April 29, 1969 6 Sheets-Sheet 5 ll I 2a- Nov. 30,1971 lSSEI IMAHASHI 3,623,428

FLYING PRINTER Filed April 29, 1969 6 Sheets-Sheet d.

Nov. 30, 1971 ISSEI IMAHASHI 3,623,428

FLYING PRINTER Filed April 29, 1969 6 Sheets-Sheet 5 United StatesPatent O 3,623,428 FLYING PRINTER Issei Imahashi, Suwa-shi, Japan,assignor to Kabushiki Kaisha Suwa Seikosha Filed Apr. 29, 1969, Ser. No.820,199

Claims priority, application Japan, Apr. 30, 1968,

43/28,688, 43/28,690; May 13, 1968, 43/31,814,

Int. Cl. B41j 9/10, 9/38 U.S. Cl. 101-93 21 Claims ABSTRACT OF THEDISCLOSURE BACKGROUND OF THE INVENTION This invention relates generallyto a printer utilized in electronic desk calculators and other numericalreadout devices. In the usual line printers, alphabetic and/ or numericcharacters, such as the numerals -9 for example, are provided incolumnar fashion on the periphery of a print drum. The drum is disposedso that the desired character in the first column faces the hammerassociated with that column, and said hammer is activated to strike theback of the paper to effect the printing of said desired character. Thedrum is then rotated to position the character desired in the secondcolumn and after the hammer associated therewith operates, the processis reported for each column on said drum. After every column hasprinted, the paper is advanced on line and the process is repeated. Inthis type of printer, the printing speed is relatively slow, as theprint drum must stop rotating each time the hammer strikes a character.

In another type of printer, generally referred to as a flying printer,the hammer strikes a character disposed on a continuously rotating printdrum. However, the known arrangements of this type of printer haveseveral substantial drawbacks. Specifically, shear will occur in theprinting process if the contact time between the hammer and the printdrum is too great, resulting in smudged printing or ripped paper. Inorder to overcome this defect, the contact time of the hammer with thecharacter must be shortened, thereby increasing the operating speed ofsaid hammer. In conventional printers of the type described, the hammeris directly operated by electromagnets, and an increase in the operatingspeed of the hammer requires an increase in the size and power of saidelectromagnets. However, an increase in the size and power of theelectromagnets results in an increase in the volume of the printer andrequires increased electric power consumption, and is thereforeundesirable. By utilizing the electromagnets to merely effect timing ofthe flying printer, rather than the actual direct operation of thehammer, the above described defects can be avoided while an extremelycompact flying printer is provided.

Other defects in the known flying printers sought to be corrected by thepresent invention are the double striking of a hammer on a single lineand the difficulty in adjusting said hammers to insure clear printing.

3,623,428 Patented Nov. 30, 1971 SUMMARY OF THE INVENTION Generallyspeaking, in accordance with the invention, a flying printer is providedhaving a trigger lever adapted for rotational and linear displacement.Said trigger lever is linearly displaced when disposed in the path of atooth of a continuously rotating ratchet wheel. When so disposed, saidtrigger lever displaces a print hammer to effect printing. Means isprovided, preferably an electromagnet, for selectively rotatablydisplacing said trigger lever into and out of the path of said ratchetwheel tooth.

The flying printer according to the invention preferably includes aprint drum which continuously rotates at a constant speed, said ratchetwheel being synchronously driven with said print drum. A trigger leverguide member, formed with a guide groove therein, and a pair of spacedguide pins are provided to guide said trigger lever in its rotationaland linear displacement. Said trigger lever is preferably formed with ashoulder adapted to strike a trigger lever stopper immediately beforesaid hammer completes striking the character on said print drum, therebylimiting the linear displacement of said trigger lever. The contactpoint between said trigger lever stopper and said trigger lever shoulderis preferably disposed above the center of gravity of said trigger leverand on the side of said trigger lever adjacent said ratchet wheelwhereby said contact tends to pivot said trigger lever out of the pathof said ratchet wheel tooth. Springs means may also be provided for thispurpose.

The cycle of linear and rotational displacement of said trigger levercommencing with the engagement thereof by said ratchet wheel tooth ispreferably slightly longer than one pitch time of the teeth of saidratchet wheel.

A flying printer according to the invention preferably includes aplurality of said trigger levers each adapted to operate a hammer leverand each in turn being provided with a separate means for effecting therotational displacement thereof into and out of the path of at least onetooth of said ratchet wheel. Said hammer levers, trigger levers,rotatable displacement means, print drum and ratchet wheel are allpreferably mounted between a pair of spaced main plates. Each of saidhammer levers is preferably L-shaped and is pivotably mounted at thecorner defined by the two arms thereof. A hammer is secured to the endof one arm of each of said hammer levers, said hammer levers beingdisposed with said hambers above the axis of said print drum with thearm thereof carrying said hammer defining the upper portion thereof. Asingle motor is provided to drive both the ratchet wheel and print drum.

Accordingly, it is an object of this invention to provide an extremelycompact flying printer adapted to print extremely clear characters.

Another object of the invention is to provide a flying printer utilizingelectromagnets to select the character to be printed, without directlyoperating the hammer.

A further object of the invention is to provide a flying printer adaptedto prevent the double printing of a character.

Still a further object of the invention is to provide a flying printerwherein the hammer is readily accessible for adjustment and replacement.

Still other objects and advantages of the invention will in part beobvious and will in part be apparent from the specification.

The invention accordingly comprises the features of construction,combinations of elements, and arrangements of parts which will beexemplified in the constructions hereinafter set forth, and the scope ofthe invention will be indicated in the claims.

3 BRIEF DESCRIPTION OF THE DRAWINGS For a fuller understanding of theinvention, reference is had to the following description taken inconnection with the accompanying drawings, in which:

FIG. 1 is a schematic representation of one column of a flying printeraccording to the invention;

FIG. 2 is a top plan view of a flying printer according to theinvention, with portions broken away;

FIG. 3 is a sectional view taken along lines 33 of FIG. 2 showing onecolumn thereof with the electromagnet associated therewith in thedeenergized state;

FIG. 4 is a sectional view taken along lines 3-3 of FIG. 2 with saidelectromagnet energized and said column disposed in the printingposition;

FIG. 5 is a side elevational view of the flying printer of FIG. 2;

FIGG. '6 is an exploded perspective view of the trigger lever andtrigger lever guide member according to the invention;

FIG. 7 is a top plan view of the trigger lever guide member according tothe invention;

FIG. 8 is a sectional view taken across the rotor of the motor of theflying printer according to the invention;

FIG. 9 is a sectional view taken along lines 99 of FIG. '8;

FIG. 10 is a sectional view taken along lines 10-10 of FIG. 8;

FIG. 11 is a circuit diagram of a driving circuit for the motor of FIG.8;

FIGS. 12A and B are wave forms present in the circuit of FIG. 11; and

FIGS. 13A, B and C are wave forms of the current in the three drivingcoils of the motor of FIG. 8.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring now to FIG. 1, aschematic representation of one column of a flying printer according tothe invention is shown. The column includes a print hammer 1 mounted onone arm of an L-shaped hammer lever 2. Said hammer lever is pivotablymounted at the corner defined by the arms thereof on hammer lever shaft3. Disposed immediately below hammer 1 is print drum 4 having charactersspaced on the peripheral surface thereof. Said print drum and a printdrum gear 5 are mounted on print drum shaft 6 for rotation therewith.Shaft 6, which defines the axis of said print drum is disposedimmediately below the position assumed by hammer 1 when it strikes saidprint drum, whereby said hammer is disposed normal to said axis whenstriking said print drum. Print drum gear 5 meshingly engagesintermediate pinion 7 for the rotation of said pinion and intermediategear 8 fixed thereto. Said intermediate gear, in turn, meshingly engageswith ratchet gear 9 for the rotation of ratchet wheel 10. Said ratchetwheel is shown formed with a single tooth 11 but could be formed with aplurality of circumferential teeth if desired. The gear ratio betweengears and pinions 5,7, 8 and 9 is selected so that the pitch time oftooth 11 equals the circumferential spacing of the characters on theperipheral surface of print drum 4. Thus, each rotation of tooth 11corresponds to the advancing of one character on said print drum.

First and second trigger lever guide pins 12 and 13 are provideddisposed on either side of trigger lever 14. Said trigger lever isformed with a tail portion 15 and a projection 16. Trigger lever 14 isadapted for pivotal and linear displacement and trigger lever guidemember 18 is provided to guide said trigger lever during saiddisplacement. A spring 19 is secured between lever 14 and a fixing point20 for biasing said trigger lever out of the path of tooth 11. The endof arm 21 of hammer lever 2 is disposed to be engaged by shoulder 22 oftrigger lever 14 upon the linear displacement of said trigger lever topivot said trigger lever, whereby hammer 1 strikes print drum 4.

Timing lever 23 is disposed to engage tail 15 of trigger lever 14 and ispivotably mounted on timing lever shaft 24. Fixed to said timing leveris magnetic plate 25 adapted to cooperate with an electromagnet 26 forthe pivoting of said magnetic plate and timing lever in response to theactivation of said electromagnet. Spring 28 is mounted between thecorner of hammer lever 2 and fixing point 29 to normally bias saidhammer lever in the position shown with hammer 1 spaced from print drum4. Interposed between said hammer and said print drum are paper 30 uponwhich the character is to be imprinted and inked ribbon 31.

In 'FIG. 1, only one column is illustrated by way of example. However,an actual printer would include the desired number of columns, each ofwhich would comprise a hammer 1, a hammer lever 2, a trigger lever 14, atrigger lever spring 19, a timing lever 23, a magnetic plate 25, anelectromagnetic 26, and a hammer lever spring 28. As more particularlyshown in the embodiment of the flying printer according to the inventionshown in FIG. 2, the parallel columns are mounted between a pair of mainplates 50 and 51. The flying printer is preferably provided with asingle print drum 4, ratchet wheel 10 having a single tooth 11, firstand second guide pins 12 and 13, trigger lever guide member 18, triggerlever stopper 17, and timing lever shaft 24, all of which extend betweensaid main plates. A motor 52 is provided to drive ratchet wheel 10,which in turn drives print wheel 5 through gears and pinions 5, 7, 8 and9.

While hammer lever 2, trigger lever 14 and timing lever 23 arerelatively thin, the electromagnets 26 are relatively bulky. In order topermit the compact mounting of the components of the flying printeraccording to the invention, said electromagnets are disposed in threebanks, as more particularly shown in FIG. 3. The electromagnetsassociated with one of each three adjacent columns forming said flyingprinter is disposed in a single bank so that space equal to the width ofthree colurns is provided for each electromagnet. The angle definedbetween magnetic plate 25 and timing lever 23 is selected in each columnaccording to the disposition of the electromagnet associated therewith.Thus, referring to FIG. 2, the electromagnet 26 associated with columnsa and b are in one bank, the electromagnets associated with colums c andd are in a second bank, while the electromagnets associated with columnsg and i are in a third bank.

Also extending between main plates 50 and 51 are a paper feeding roller53 and guide frames 54 and 55 adapted to guide paper 30 through saidflying printer. Said paper feeding roller advances the paper one linewhen print drum 4 has completed one cycle of its rotation.

Turning now to the operation of the flying printer according to theinvention, reference is had to FIGS. 1, 3 and 4. When the flying printeris activated but no timing signals are applied to the electromagnets orto the paper advance mechanism, motor 52 continuously rotates ratchetwheel 10 in the direction of arrow 32, thereby also rotating print wheel4 in the manner described above. Said print wheel rotates in the samedirection as said ratchet wheel. The rotation of tooth 11 of saidratchet wheel follows a path defined by dashed line 33. In the absenceof any signal energizing electromagnet 26, the column is disposed asshown in FIG. 3 with end 34 of trigger lever 14 disposed outside of thepath of tooth 11 and maintained in that position by spring 19. When sodisposed, trigger lever 14 is positioned by means of second triggerlever pin 13 and trigger lever guide member 18. Magnetic plate 25 isalso maintained spaced from electromagnet 26 in the direction of arrow35 by spring 19 acting through tail 15 of said trigger lever whichengages timing lever 23.

In order to print a character, a pulse signal is applied toelectromagnet 26 immediately before the desired character on theperipheral surface of print drum 4 passes under hammer 1. The activationof said electromagnet rotatably displaces magnetic plate 25 in thedirection of arrow 36, carrying timing lever 23 therewith. Said timinglever engages the tail 15 of trigger lever 14 to rotate said triggerlever in the counter clockwise direction about trigger lever guidemember 18. When so disposed, as shown in FIG. 1, end 34 of said triggerlever lies in the path of tooth 11, whereby it may be linearly displacedin the direction of arrow 37 thereby.

The linear displacement of trigger lever 14 is transmitted to arm 21 ofhammer lever 2 by means of shoulder 22 of said trigger lever. Saidhammer lever is in turn rotated in a counter clockwise direction causinghammer 1 to strike the print drum through inked ribbon 31 and paper 30at the moment that the desired character is positioned under saidhammer. The column is shown disposed in this position in FIG. 4.

At this point in the cycle, it is necessary to rotate hammer lever 14 inthe clockwise direction to bring end 34 thereof out of the path 33 oftooth 11 before said tooth completes a single revolution. If this is notdone, the trigger lever will be linearly displaced in the direction ofarrow 37 a second time during the next revolution of ratchet wheel 10,resulting in the double striking of hammer 1 on a single line. Severalfeatures of the flying printed according to the invention contribute tothis result. The first of these is trigger lever stopper 17 whichcooperates with projection 16 on trigger lever 14, to operate asfollows. At the moment that end 34 of said trigger lever is struck bytooth 11, hammer lever 2 starts its rotation. Specifically, at themoment that said trigger lever is struck by said tooth, said triggerlever starts its linear displacement in the direction of arrow 37 at aspeed slightly faster than that of said tooth. At the same moment, arm21 of hammer lever 2 starts its displacement at a speed slightly fasterthan that of said trigger lever. This results from the fact that thecoefficient of restitution at each striking point is not equal to zero.Further, after hammer 1 strikes the desired character, hammer lever 2returns to its original position at a faster speed than does triggerlever 14. Accordingly, in the absence of trigger lever stopper 17, arm21 of said hammer lever would tend to again strike shoulder 22 of saidtrigger lever, causing said hammer lever to again rotate in theclockwise direction causing hammer 1 to again strike a character. Theresulting double striking on a single line is of course undesirable.This possibility is avoided by the striking of projection 16 againsttrigger lever stopper 17 immediately before hammer 1 strikes thecharacter so that trigger lever 14 rebounds in the direction of arrow 38before the return of hammer lever 2 to its original position. In thismanner, arm 21 of said hammer lever will not strike shoulder 22 duringsaid return.

The striking of projection 16 against trigger lever stopper 17 alsoserves to rotate said trigger lever in the direction of arrow 39 aboutthe center of gravity 40 of said trigger lever during the return thereofto its initial position. This effect, which serves to bring end 34 ofsaid trigger lever out of the path of tooth 11, results from thepositioning of the contact point between said projection and saidtrigger lever stopper at a position above center of gravity 40, andpreferably on the side of said center of gravity adjacent to ratchetwheel 10. Also contributing to this rotation is spring 19 which tends toreturn said trigger lever to its original position with the innersurface of shoulder 22 resting against trigger lever guide member 18 andend 34 of said trigger lever out of the path of tooth 11.

Still a further feature of the arrangement according to the inventiontending to avoid double striking, is the timing of the arrangement. Eachcycle of operation, namely the activation of an electromagnet, thelinear displacement of trigger lever 14, the striking of hammer 1 andthe return of said trigger lever takes an extremely short time, of theorder of 7 ms. Despite all of the above described features, it is stillpossible, in rare cases, that end 34 of said trigger lever might stilllie within the path of tooth 11 if said trigger lever returns to itsoriginal position before tooth 11 has completed one cycle or pitch time.If this were so, undesirable double striking would result. Accordingly,the ararngement according to the invention is designed so that the timerequired for trigger lever 14 to complete one cycle of operationcommencing with the linear displacement thereof by tooth 11 and endingwith its return to its original position, is slightly longer than thepitch time of the tooth of said ratchet wheel. The timing of the overallarrangement is such that a particular column would never be activated tostrike two consecutive characters on the print drum in a single cycle ofsaid print drum.

Referring now to FIGS. 6 and 7, a detailed View of trigger lever guidemember 18 is shown. Said member is formed with a plurality of grooves 41defined by walls 42 adapted to receive said trigger levers and to guidesame during the rotational and linear displacement thereof.

As shown in FIGS. 2 and 3, arms 43 of hammer levers 2, upon whichhammers 1 are mounted, defines the upper level of the flying printeraccording to the invention. In this manner, hammer 1 is disposedimmediately above the axis of print drum 4 as defined by shaft 6. Thisconstruction permits easy access to hammers 1 to permit the replacementor adjustment thereof. The latter feature is important since in order toprint clear characters, the face of the hammer and the surface of thecharacter must lie in the same plane, the striking point and the desiredcharacter must exactly coincide, and uniform pressure must be applied tothe surface of the character to be printed. Further, of the componentsof the flying printer according to the invention, said hammers aresubjected to the greatest wear due to the extremely fast striking speed,and therefore require replacement after an extended period of use. Suchreplacement may be accomplished without disturbing the other componentsof the column. Finally, this feature permits the immediate and readydetection of misprints since the operator can see each characterimmediately after the paper is ad vanced one line.

The detailed structure of motor 52 is shown in FIGS. 810. Said motor,which is of the direct current brushless type includes a rotor shaft 56having yokes 57 and 58, formed of a material having high permeabilitymounted thereon in spaced relation. Arranged radially about shaft 56 arepairs of permanent magnets 59 and 65, 60 and 66, 61 and 67, 62 and 68,63 and 69, and 64 and 70. One of each of said pairs of electromagnets,namely magnets 59, 60, 61, 62, 63 and 64, are fixedly secured to yoke57, while the other of said permanent magnets are fixedly secured toyoke 58. Each of said permanent magnets is fan shaped. Each of saidpairs of permanent magnets are in spaced relation and disposed withopposite poles in facing relation. Thus, the south pole of magnet 62faces the north pole of magnet 68. Further, the six poles secured toeach yoke are disposed so that adjacent magnets have their oppositepoles facing the air gap between said pairs of permanent magnets. Thus,permanent magnet 59 has its north pole facing the air gap and itscompanion permanent magnet 65, while the adjacent permanent magnets 60and 64 both have their south poles facing said air gap and theirrespective companion magnets.

Disposed in the air gap between said pairs of permanent magnets aresubstantially trapezoidal flat driving coils 71, 72 and 73. Said drivingcoils are radially arranged about rotor shaft 56 but are mountedindependently thereof. Said driving coils are spaced degrees apart asmeasured from their respective centerlines. The sides 74 and 75 of eachdriving coil are spaced so that one of said sides is disposed in thespace between each of two adjacent pairs of permanent magnets insubstantially all positions of rotor shaft 56. Thus, in FIG. 9, side 74of driving coil 73 is shown disposed in the space between the pair ofpermanent magnets 60 and 66 while side 75 of driving coil 73 is disposedbetween the pair of permanent magnets 61 and 67. In the position shown,driving coil 71 is aligned with the gaps between adjacent pairs of saidpermanent magnets while the other of said driving coils are aligned asdescribed above.

Also provided is a detecting means consisting of three pairs ofdetecting coils 76 and 77, 7-8 and 79, and 80 and 81, as moreparticularly shown in FIG. 10. Said detecting coils are preferablyformed in the shape of small discs with the detecting coils forming eachpair being disposed in spaced relation with an air gap therebetween.Said pairs of detecting coils are disposed radially about rotor shaft 56with an angle of 40 degrees being defined between pairs 75 (77) and 78(79), and 80 (81), respectively. Said detecting means also includes ashield plate 82 fixedly mounted to rotor shaft 56 and extending into thegap between said pairs of detecting coils. The shield plate is formedwith three cut-away regions 83 within the path of said detector coil airgaps. Said cut-away regions are spaced radially about rotor shaft 56,each of said openings defining a 40 degree sector. Shield plate 82 ispreferably formed from a material of low electric resistance, such asaluminum.

Re ferring now to FIG. 11, a portion of the electric circuit for drivingone driving coil 71 of motor 52 is shown by way of example. The circuitincludes an oscillator formed from transistor 84 and detecting coils 76and 77. The output of the oscillator passes through a rectifier definedby diode 85 and is applied to an amplification and switching circuitdefined by transistors 86 and 87 adapted to apply driving current todriving coil 71.

Reference is now had to the wave form diagrams of FIGS. 12 and 13, inconnection with which the operation of the br-ushless direct currentmotor according to the invention will be exemplified. Assuming that oneof the cut-away regions of shield plate 82 is disposed at the pair ofdetecting coils 76 and 77, the oscillator circuit associated with saiddetector coils starts to oscillate to produce the wave form shown inFIG. 12A at the collector of said transistor. This oscillating wave hasa pulse width of T equal to the period during which the opening 83 inshield plate 82 is positioned opposite detecting coils 76 and 77. Theoscillating circuit is rectified by diode 85 to produce, at connectingpoint 88 of FIG. 11, the driving wave form shown in FIG. 12B. During theperiod T transistors 86 and 87 are switched on to apply driving currentto driving coil 71. The oscillator circuit stops oscillating when shieldplate 82 extends into the gap between detecting coils 76 and 77 sincesaid shield plate is formed of a conductor. The driving current indriving coil 71 interlinks with the magnetic flux of the pairs ofpermanent magnets between which the sides 74 and 75 of said coil extend.Accordingly, a rotational force is produced tending to rotate shaft 56,carrying yokes 57 and 58, the permanent magnets, and shield plate 82therewith. The time T shown in the wave form of FIG. 12A represents theperiod during which the shield plate extends into the gap between thepair of detecting coils to stop the oscillation thereof. The cycle, asfar as detecting coils 76 and 77 and driving coil 71, is repeated afterthe time T as represented by the rotation of the rotor by 80 degress toalign the next cut-away region of the shield plate with said detectingcoils.

In the embodiment of the arrangement shown in the drawings, three pairsof detecting coils and three corresponding driving coils are provided.Accordingly, the motor according to the invention would be provided withthree transistorized driving circuits. Each of the three drivingcircuits drives a driving coil to produce three phases of drivingcurrent as shown in the wave forms of FIGS. 13A, B and C, one of whichrepresents the current in each of said driving coils. Due to therelative position of the detecting coils, driving coils, and shieldplates and the alignment of the poles of the permanent magnets, rotor 1always rotates in the predetermined direction.

The pairs of detecting coils are arranged radially about shaft 1 so thatthe cut-away region of shield plate 31 is aligned with at least one ofsaid pairs of detecting coils at every position of said rotor shaft.Thus, one of said pairs of coils oscillates at each such position todrive the driving coil associated therewith. Further, said driving coilassociated with the oscillating detecting coils must be disposed sothat, during the period of said oscillation, it is not aligned with onlyone of the pairs of permanent magnets. This arrangement is necessary toinsure that the motor is self starting since if a driving coil isaligned with only one pair of permanent magnets at the rest position, norotating force will be generated in response to the oscillation of thedetecting coils to start the motor.

Although the motor in the embodiment shown in the drawings has six pairsof permanent magnets, three driving coils, three pairs of detectingcoils and three cutaway regions in the shield plate, this arrangement isshown by way of example and not by way of limitation, and the motoraccording to the invention may be designed with various combinations ofcoils and openings. In general, the motor should be constructed suchthat where n pairs of permanent magnets are provided, it being an evennumber equal to six or more, n/2 driving coils, n/ 2 pairs of detectingcoils, an n/2 cut-away regions of the shield plate are provided.Further, the detecting coils of the detecting means may consist of onlya single oscillating coil the oscillation of which can be stopped bybringing said shield plate into juxtaposition with said coil.

As best shown in FIG. 2, driving coils 71, 72 and 73 are fixedly mountedon a circuit board 89. In like manner, detecting coils 76, 78 and 80 aremounted on a circuit board 90, While detecting coils 77, 79 and 81 aremounted on a circuit board 91. The foregoing construction produces anextremely compact motor capable of producing suflicient force to operatethe flying printer according to the invention.

Turning now to FIGS. 2 and 5, the overall operation of the flyingprinter according to the invention will be described. Rotor shaft 56 ofmotor 52, upon which ratchet wheel 10 is mounted, carries at one endthereof a position detector having a magnet 101 mounted on theperipheral surface thereof which generates timing signals with everyrotation, said timing signals being detected by a magnetic pickup head102. The rotation of rotor shaft 56 and ratchet Wheel 10 is transmittedto print drum 4 for the rotation thereof and synchronization with saidratchet wheel. As discussed above, one rotation of ratchet wheel 10equals the advancing of print drum 4, one character. Thus, if there aresixteen characters circumferentially spaced about print drum 4, ratchetwheel 10 will rotate sixteen times for every rotation of print drum 4.Mounted on one end of shaft 6 which carries said print drum is positiondetector 103, also provided with a magnet in the peripheral surfacethereof to provide timing signals for detection by magnetic pickup head104. The timing signals detected by magnetic head 102 are preferablycounted by a suitable pulse counter which operates in conjunction with acoincidence circuit adapted to compare the input signals from thecircuitry of the desk calculator or other device to which the printer isconnected with the detected signal. When coincidence is detected, theelectromagnet associated with said circuit is energized to effectprinting.

The timing signals detected by magnetic head 104 are used for resettingthe flying printer to permit printing of the next line. Said resetsignal provides clock pulses to suitable controlling circuitry whichpermits both the resetting of the character counter and the energizationof paper feeding electromagnet 105 which displaces hooked lever 106 torotate ratchet 107 and paper feeding roller 53 to shift said paper byone line.

It has been found that a flying printer constructed in accordance withthe invention offers substantial advantages over the prior art. Thus,although printing is performed during the continuous rotation of theprint drum, the period of dwell of the hammer is shortened and clearlyprinted characters are obtained. The arrangement minimizes the wear onthe trigger lever utilized to transmit energy to the hammer, giving suchtrigger lever an extremely long life. Since said trigger lever ispreferably formed from a material of great stiffness, the operation ofthe arrangement results in a relatively low energy loss during highspeed operation. Further, the arrangement avoids the defect of doublestriking, and provides an arrangement which is readily serviced.

Further, the arrangement according to the invention provides a devicewhich consumes relatively little electric power, while utilizing asingle motor to drive the entire mechanism including both the ratchetwhee-l and print drum. The arrangement according to the invention ineffect, converts the rotational kinetic energy stored in the ratchetwheel to linear energy by the unique action of the trigger levers whichare pulsively actuated by the rotating tooth to provide a large amountof mechanical energy to the print hammers without requiring largeelectromagnets.

It will thus be seen that the objects set forth above, among those madeapparent from the preceding description are efliciently attained and,since certain changes may be made in the above construction withoutdeparting from the spirit and scope of the invention, it is intendedthat all matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:

1. A flying printer which comprises a continuously rotating ratchetwheel having at least one tooth extending therefrom; a print drumcontinuously rotating synchronously with said ratchet wheel; a triggerlever mounted for rotational and linear displacement along a path, saidtrigger lever path being positioned so that at one point therea-long,said trigger lever lies in the path of said ratchet wheel tooth and islinearly displaced thereby out of said ratchet wheel tooth path; printhammer means displaceably mounted in said trigger lever path foreffecting printing in response to said linear displacement of saidtrigger lever actuated by said ratchet wheel tooth, means forselectively rotating said trigger lever from an initial position intosaid ratchet wheel tooth path; a fixed trigger lever stopper disposed insaid linear displacement portion of said trigger lever path, saidtrigger lever having a portion adapted to strike said trigger leverstopper immediately before said print hammer means effects printing;spring means secured to said trigger lever and biased to rotatably andlinearly displace said trigger lever back to said initial position outof the path of said ratchet wheel tooth after rebound of said triggerlever from said trigger lever stopper; and guide means in said triggerlever path for freely guiding said trigger lever along a rotational andlinear portion of said trigger lever path in conjunction with saidspring means after said rebound from said trigger lever stopper.

2. A flying printer as recited in claim 1, wherein said print hammermeans includes a hammer lever mounted for rotational displacement at acentral region thereof and a hammer mounted for printing on said hammerlever on one side of said central region and spaced therefrom, saidtrigger lever, upon the linear displacement thereof, engaging saidhammer lever at a point disposed at the other side of said centralregion and spaced therefrom to rotatably displace said hammer lever toeffect printing.

3. A flying printer as recited in claim 1, wherein said means forselectively rotating said trigger lever includes an electromagnet and atiming lever mounted for rota- 10 tional displacement, said timing leverbeing rotatably displaced in response to the energization of saidelectromagnet to rotatably displace said trigger lever into the path ofsaid ratchet wheel tooth.

4. A flying printer as recited in claim 1, including a print drumadapted for continuous rotation at a constant speed, said ratchet wheelbeing adapted for rotation in synchronization with said print drum, saidprint hammer means including a print hammer for striking said print drumto effect printing.

5. A flying printer as recited in claim 1, wherein the contact pointbetween said trigger lever portion and said trigger lever stopper isdisposed above the center of gravity of said trigger lever.

6. A flying printer as recited in claim 5, wherein the contact pointbetween said portion of said trigger lever and said trigger leverstopper is disposed on the side of said center of gravity adjacent saidratchet wheel.

7. A flying printer as recited in claim 1, wherein said guide meansincludes a trigger lever guide member formed with a groove therein, saidtrigger lever being positioned in said guide groove and rotating aboutthe bottom surface thereof.

8. A flying printer as recited in claim 1, including a first triggerlever guide pin disposed to position said trigger lever in the path ofsaid ratchet wheel tooth upon the rotational displacement thereof and asecond trigger lever guide pin disposed to position said trigger leverat said initial position out of the path of said ratchet wheel tooth.

9. A flying printer as recited in claim 1, wherein said print hammermeans includes a substantially L-shaped hammer lever rotatably mountedat the corner defined by the two arms thereof, and a print hammermounted on one of said hammer lever arms for printing, said triggerlever being adapted to engage the other of said hammer lever arms uponthe linear displacement thereof by said ratchet wheel tooth to rotatablydisplace said hammer lever to effect printing.

10. A flying printer as recited in claim 1, wherein said spring means isconstituted to have a coeflicient of flexibility, and said trigger leveris constituted to have a mass, such that a cycle of said linear androtational displacement of said trigger lever along its path from saidinitial position and back to said initial position is slightly longerthan one pitch time of the tooth of said ratchet wheel.

11. A flying printer as recited in claim 1, including unitary motormeans for driving both said print drum and said ratchet wheel.

12. A flying printer as recited in claim 11, including a gear traininterconnecting said ratchet wheel and said print drum for transmittingthe motor force of said motor means from one to the other.

13. A flying printer as recited in claim 11, wherein said motor meansincludes a rotor shaft, a pair of spaced yokes mounted on said shaft forrotation therewith, a plurality of pairs of permanent magnets radiallyarranged about said shaft between said yokes, one of each of said pairsof permanent magnets being mounted on each of said yokes with a gaptherebetween; a plurality of driving coils disposed in the gap betweensaid pairs of permanent magnets; and a detecting means responsive to theposition of said rotor shaft and having at least one detecting coilassociated with each driving coil for the activation of said drivingcoil to rotate said rotor shaft.

14. A flying printer as recited in claim 13 wherein the poles of eachpair of permanent magnets defining the gap therebetween are of oppositepolarity to produce a magnetic field in said gap.

15. A flying printer as recited in claim 13, wherein, at each positionof said rotor shaft, the driving coils activated at said position haveportions disposed in the gap defined by selected pairs of permanentmagnets, all of said pairs of permanent magnets being selected toproduce a force on said rotor shaft in a predetermined direction.

16. A flying printer as recited in claim 1, wherein the contact pointbetween said trigger lever portion and said trigger lever stopper isdisposed above the extension line of the path of the motion of thecenter of gravity of said trigger lever.

17. A flying printer as recited in claim 16 wherein the contact pointbetween said portion of said trigger lever and said trigger leverstopper is disposed on the ratchet wheel side of the extension line ofthe path of the motion of the center of gravity of said trigger lever.

13. A flying printer having a continuously rotating print drum, aratchet Wheel having at least one tooth, means for continuously rotatingsaid ratchet wheel and print drum in synchronization with each other,and at least one printing column including a trigger lever adapted forrotational and linear displacement along a path, said trigger lever pathbeing positioned so that at one point therealong, said trigger leverlies in the path of said ratchet wheel tooth and is linearly displacedthereby out of said ratchet wheel tooth path; a hammer lever mounted insaid linear displacement portion of said trigger lever path forrotational displacement in response to said linear displacement of saidtrigger lever; a print hammer mounted on said hammer lever for strikingsaid print drum to effect printing upon the rotational displacement ofsaid hammer lever; means for selectively rotating said trigger leverfrom an initial position into the path of said ratchet wheel tooth; afixed trigger lever stopper disposed in said linear displacement portionof the path of said trigger lever, said trigger lever having a portionadapted to strike said trigger lever stopper immediately before saidprint hammer means effects printing; spring means secured to saidtrigger lever and biased to rotatably and linearly displace said triggerlever back to said initial position out of the path of said ratchetwheel tooth after rebound of said trigger lever from said trigger leverstopper; and guide means for 1.2 guiding said trigger lever along arotational and linear portion of said trigger lever path in conjunctionwith said spring means after said rebound from said trigger leverstopper.

19. A flying printer as recited in claim 18, wherein said hammer leveris substantially L-shaped and pivotably mounted for rotativedisplacement about the corner defined by the two arms thereof, saidprint hammer being mounted on one arm of said hammer lever, said armbeing disposed above said trigger lever, ratchet wheel and print drumwith said hammer positioned to strike said print drum to effect printingat a point above the longitudinal axis of said print drum.

20. A flying printer as recited claim 18, wherein said flying printerincludes a plurality of printing columns disposed in side-by-siderelation along said print drum and ratchet wheel.

21. A flying printer as recited in claim 20, wherein the print hammer ofeach of said printing columns is disposed above said print drum inposition to strike said print drum at a point above the longitudinalaxis thereof, the portion of each hammer lever upon which said printhammer is mounted defining the top of each of said columns.

References Cited UNITED STATES PATENTS 2,766,686 10/1956 Fomenko et al.10193 2,897,752 8/1959 Malmros et. a1 101-93 2,949,846 8/1960 Hoffman etal. 10193 3,139,820 7/1964 Kittler l0193 3,156,180 11/1964 Barnes 10l933,177,803 4/1965 Antonucci 10193 3,292,531 12/1966 Mutz 10193 3,351,00711/l967 Poland 101-93 3,504,623 4/1970 Staller 101-93 WILLIAM B. PENN,Primary Examiner

